Model development and control methodology of a new electric power steering system

Abstract

In this study, a new column-type electric power steering (EPS-TT) system is investigated. The remarkable features of this EPS-TT system are its opto-isolated torque sensor, which is used to make steering torque measurements, and its assist torque control methodology, which uses a unidirectional motor and two clutches. Thus it does not require a complicated motor drive system that consumes a large amount of electrical energy when the direction of rotation is reversed. This allows the new system to use a smaller and simpler assist motor. A full steering system model and a simplified model are developed to evaluate the EPS-TT system. A full car model is also used to investigate the vehicle response. A map-based control method and a proportional-integral-derivative control algorithm are designed to control the EPS-TT system. Various sinusoidal inputs are applied to the system and the resulting performance is analysed. The results show that the performance achieved by the EPS-TT system is similar to that of a conventional EPS system across the frequency domain. The results for the full steering system model are similar to those for the simplified model, but the vehicle response is slightly different. The map-based controller provided good performance without affecting the stability or controllability of the vehicle.

Comparison between braking and steering yaw moment controllers considering ABS control aspects

“…1) [7] and a simplified electric power steering system model ( Fig. 2) [8]. The vehicle model is constructed from many sub-models, such as the powertrain, suspension, tyres, chassis, road conditions, and so on, and the effect of each sub-system should be considered.…”

“…(1)-(3) is 1, 2, 3 and 4, and represents the front left, front right, rear left, and rear right wheels, respectively. m total is the total mass of the vehicle, which consists of the sprung mass (m s ), front unsprung mass (m uf ), and rear unsprung mass (m ur ) [5,8].…”

“…Simplified electric power steering system model From Fig. 2 and Newton's second law, the torques applied on the steering column and pinion of an electric power steering system can be calculated by [8]:…”

Enhanced braking and steering yaw motion controllers with a non-linear observer for improved vehicle stability

“…Figure 1 depicts the overall vehicle system model. Detailed information about the models is not included in this paper because it has been published elsewhere [7,10,11]. Figure 2 shows a vehicle that consists of a chassis, tyres, and brakes.…”

“…The braking pressure is calculated and applied to each wheel independently. The desired slip of the ABS is assumed to be 0.2 when the vehicle is on a straight road, regardless of the road conditions [5,10]. However, if the vehicle is on a curved or split-m road, where the yaw rate differs from the reference yaw rate, the EBYMC or ESYMC is engaged and the desired slip is changed.…”